Field of the Invention
The disclosure relates to generally to devices and methods for the preservation of substances and object that are sensitive to oxygen and humidity. More specifically, certain foods, pharmaceuticals, botanicals and herbs may benefit.
Description of the Related Art
Many foods and botanicals or herbs, such as cannabis, are most stable and best consumed at a certain water activity. These substances are also subject to degradation due to the chemical reaction of certain components with oxygen found in the surrounding atmosphere frequently called headspace. For example, the unsaturated lipids in food products and the terpenes in cannabis readily react with molecular oxygen to form undesirable oxidation products, thus degrading the quality and even the efficacy of the food or botanical.
As disclosed in U.S. Pat. No. 5,936,178, the relative humidity of closed environments can be stabilized by the use of humidity control systems comprised of moisture permeable pouches containing specific salt solutions. Also, certain non-ionic solutions containing low molecular weight molecules such as ethylene glycol, propylene glycol, glycerin, urea, guanidine, ethanol amine, simple sugars, or sugar alcohols may be employed. The choice of the solute and the solute concentration in an aqueous solution determines the solution water activity (aw). A solution of a certain water activity will equilibrate with the surrounding atmosphere until the relative humidity (RH) is equivalent to the water activity multiplied by 100. That is, the RH percentage will equal the water activity×100. For example, an aqueous solution of saturated sodium chloride with excess crystals, aw 0.75 will equilibrate with the moist air or dry air in a closed system until a relative humidity of 75 percent is achieved.
The moisture transfer capacity (MTC) is defined as the amount of moisture transferred, into or out of, a given control system, i.e. device, pouch, etc., over a defined relative humidity range. For example, a saturated solution of sodium chloride can transfer about 65% moisture, maintaining a water activity of 0.75. Clearly an aqueous system would be required to have sufficient MTC to maintain the RH of certain products.
The choice of salt solution is not only important because of its ability to define the relative humidity, the salt must not chemically degrade the pouch film construction or emit, outgas, corrosive or obnoxious substances.
A number of dry oxygen absorbing packets are currently marketed. These include brand names like AGELESS®, StayFresh® and FreshPax®. The technology is based on the chemical reaction of oxygen with a metal, typically iron. U.S. Pat. No. 4,127,503 describes this technology and is incorporated herein in its entirety by reference. More recently, U.S. Pat. No. 8,048,201, also incorporated herein in its entirety by reference, discloses a system comprised of a wicking agent, malic acid and iron at pH 2 to 3. The wicking agent absorbs atmospheric water and activates the acid which reacts with iron to consume oxygen. These systems are very efficient and are commonly employed to decrease headspace oxygen in a variety of applications. These systems, however, are not dual action humidity and oxygen control. These oxygen scavenger systems are packaged in films that are readily permeable to oxygen, but not necessarily suitable to fulfill the dual function of humidity control and oxygen elimination disclosed in this patent.
Further, in U.S. Pat. No. 6,921,026, commonly owned by the current assignee Boveda, Inc., Saari discloses a method for the dual control of headspace humidity and oxygen comprised of an aqueous salt solution and elemental iron. U.S. Pat. No. 6,921,026 is incorporated by reference herein in its entirety. While this method controls humidity, the rate of oxygen reaction with the metal is too slow to be of commercial value and, therefore, is susceptible to improvement. Ascorbic acid salts chemically react with molecular oxygen to form hydrogen peroxide and dehydroascorbic acid salts. The hydrogen peroxide is consumed by further reacting with ascorbic acid, dehydroascorbic acid salts to form tetahydroxydiketohexanoic acid salts. See Deutsch, J C, Anal. Biochem, 1998, Jan. 1; 255(1):1-7, also incorporated herein in its entirety by reference. Clearly isomers of ascorbic acid such as erythorbic acid salts will behave in a similar fashion.
While this ascorbate oxidation reaction has been employed to remove dissolved oxygen from boiler water as taught by U.S. Pat. No. 4,891,141, incorporated herein in its entirety by reference, the use of this reaction mixed with inorganic salts to decrease headspace oxygen has not been reported. Furthermore, it was discovered that metallic iron in conjunction with the ascorbate salt increased the rate of oxygen headspace removal.
Accordingly, there exists a need for an improved method to control headspace humidity and oxygen by combining certain salt solutions with ascorbic acid salts or isomers thereof alone or in combination with iron between pH 6 and 10.